Christina Aguilera set social networks buzzing when she fluffed a line as she belted out the national anthem at the start of the US Super Bowl.

The singer was supposed to sing the Star Spangled Banner line "O'er the ramparts we watched, were so gallantly streaming", but instead repeated an earlier line, with a slight variation.

She sang: "What so proudly we watched at the twilight's last gleaming" - the same line from earlier in the song but with the word "watched" instead of "hailed".

The mistake immediately sparked a host of comments on social network sites.

Christina said later she made the gaffe after getting lost in the moment.

She said: "I can only hope that everyone could feel my love for this country and that the true spirit of it's anthem still came through."

The football field was not the only place fans spotted stars at the Super Bowl - there were plenty of famous faces in the crowd at the Cowboys Stadium in Dallas, Texas, to watch the match between the Pittsburgh Steelers and the Green Bay Packers.

Hugh Jackman, John Travolta, Adam Sandler, Jennifer Aniston and Catherine Zeta-Jones and husband Michael Douglas were among the famous-name spectators. Owen Wilson and Jamie Foxx - who both grew up in North Texas - were also there.

Keith Urban and wife Nicole Kidman's second daughter, five-week-old Faith, joined her two-year-old sister, Sunday, at the stadium, where singer Keith and Maroon 5 gave a pre-game concert.